1. Field of the Invention
The present invention relates to a gasket and its manufacturing method, and more particularly to a gasket which can easily and securely obtain a sheet-like gasket having a good sealing performance, and a manufacturing method for the gasket.
2. Description of the Conventional Art
Conventionally, in order to seal a gap between housings in an engine cam cover, a fuel cell, an electronic device and the like which are made of a resin material, a gasket made of a rubber-like elastic material has been used in the gap.
Further, as one example of this kind of gasket, a structure having a shape shown in FIG. 16 has been proposed (refer to Japanese Unexamined Patent Publication No. 2009-299903).
However, in this kind of gasket, since a chevron gasket portion 200 is formed on a surface of a base material 100 such as a metal material, a resin material or the like by using a metal mold, a sealing performance is good, however, it is necessary to prepare the metal mold per one specification, so that a problem that a manufacturing cost is increased has been brought about.
Accordingly, there has been proposed a sheet-like gasket structured, as shown in FIG. 17, such that a gasket portion 200 made of a rubber-like elastic material and having a fixed uniform thickness is bonded on a surface of a sheet-like base material 100 (refer to Japanese Unexamined Patent Publication No. 11-37294).
Since this kind of gasket can be provided for various intended uses only by punching the sheet-like gasket in correspondence to the specification, it has an advantage that the gasket can be provided inexpensively.
However, since the gasket comes into contact with the other surface to be sealed in a wide plane state, a high repulsive force is brought about with respect to the other member, and in the case that the other member is thin or fragile such as a resin material, a problem that the other member is deformed has been brought about.
Further, since the following property to the other member is low, a problem that the sealing performance is lowered at an early time due to a permanent strain of the rubber-like elastic material has been brought about.
Further, in the case that the sheet-like base material 100 having a low rigidity is used, and the gasket portion 200 is simultaneously formed on both front and back surfaces, it is hard to keep the sheet-like base material 100 at a planed position without deforming. Therefore, since it is necessary to form one surface by one surface, a low cost formation has been prevented.